It really annoys me when I come to a Web form and the drop-down for US states reads: "AL", "AK", "AS", "AZ", "AR", and so on. How many people can really tell, without looking it up, what "MH" stands for? (Marshall Islands).
If your drown-down consists of the abbreviations, you have problems. First, you're lazy. That doesn't bode well when I think about how much effort you may have put into security. More and more I've learned, if it looks amateurish, it probably is. Lack of pride and lack of quality frequently go hand in hand.
The programmer in question might argue "so what? Everyone knows their own state abbreviation." When I type an "O" into such a drop down, "OH" and "OK" come up before "OR". It's much easier for me to notice when a drop-down says "Ohio" or "Oklahoma" instead of "Oregon". In other words, it makes it easier for me to find and correct mistakes. However, that still doesn't take into account the fact that it may not be my state. What if it's a "ship-to" address? Puzzling through the list can get awfully annoying.
Of course, it's possible they have good state detection via zip codes, but it still doesn't fix the last problem: it's just plain ugly. Please folks, take a few minutes to get this right. You'll be glad you did.